1. Field of the Invention
This invention relates to a wire connection structure in which a covered wire is placed on a terminal and ultrasonic wave energy is applied thereto with a pressure so as to melt a cover portion of the wire thereby making core elements and a terminal into conductive contact with each other.
2. Description of Relevant Art
This kind of art has been disclosed in, for example, Japanese Patent Publication No.7-70345. FIGS. 1 are explanatory views for explaining that art while FIG. 1A shows a first member 1 and a second member 2. Both the members 1, 2 are formed of material (plastic) which can be fused by ultrasonic vibration. The first member 1 contains groove portions 3 and the second member 2 includes protrusions 4 which engage the groove portions 3.
FIGS. 1B, 1C show a state in which a terminal 7 is contained in a groove portion 3 and a covered wire 8 is placed thereon. At a bottom face of the groove portion 3 are formed small concave portions 3a and at a top face of the protrusion 4 are formed small protrusions 4a which engage the small concave portions 3a.
According to this art, as shown in FIGS. 1A, 1B, the terminal 7 is contained in the groove portion 3 and the covered wire 8 is placed thereon. Then, the second member 2 is mounted on a top face of the first member 1 such that the protrusions 4 are inserted into the groove portions 3. By applying ultrasonic vibration between the first and second members 1, 2 with a pressure, a cover portion of the covered wire 8 nipped between the protrusion 4 and groove portion 3 is melted so as to make the core elements of the covered wire 8 and the terminal 7 into conductive contact with each other. At the same time, the first and second members 1, 2 are fit to each other by fusion, so that an integrated connection structure as shown in FIG. 1D is obtained.
However, according to the aforementioned prior art, as shown in FIG. 2, the melted cover portion 8b escapes into a gap between the groove portion 3 and a side face of the protrusion 4. At this time, if some of the core elements 8a escape sideways together with the melted cover portion 8b, an excellent conductive contact between the core elements 8a and terminal 7 cannot be obtained.
Although as a countermeasure, a method of eliminating a gap between the groove portion 3 and the side face of the protrusion 4 as shown in FIG. 3 can be considered, if the side faces of the groove portion 3 and protrusion 4 are in contact with each other, ultrasonic wave is not transmitted excellently to a target position (covered wire 8 on the terminal 3), so that processing efficiency may be deteriorated. Further, because the escape space for the melted cover portion 8b is limited to only the length direction of the groove portion 3, engagement between the first and second members 1, 2 becomes incomplete, so that there is a fear that an excellent conductive contact between the core elements 8a and terminal 7 may not be obtained.